There are things common to all the "heroic" polonaises (opp. 44, 53 and 61) but for now, a basic analysis of opus 53's form.
This polonaise has an extended introduction, bar 1-16, followed by the main theme, "A" from bars 17-32, then a return to "A" at bar 33-48, as an expanded variation. Next we find a couple of thematic bridges at bars 49-56 and bars 57-64. At bar 65-80, we again see the registerally, harmonically, dynamically and texturally expanded version of theme "A". An ostinato section (with repeat) follows from bar 80-120. At bar 121-128 we encounter another thematic bridge, which segues neatly into theme "B", which meanders chromatically between bar 129-154 until, with some impetus, we're lead into the triumphant return of that expanded variation of "A" through bars 155-170. All this comes crashing down at bar 171-181 with the drama of the coda.
I wonder. Why the long intro?